Computer systems are fundamentally comprised of subsystems for storing and retrieving information, manipulating information, and displaying information. Nearly all computer systems today use optical, magnetic or magneto-optical storage media to store and retrieve the bulk of a computer system's data. Successive generations of ever more powerful microprocessors, and increasingly complex software applications that take advantage of these microprocessors, have driven the storage capacity needs of systems higher and have simultaneously driven read and write performance demands higher. Magnetic storage remains one of the few viable technologies for economically storing large amounts of information with acceptable read and write performance.
Market pressures place ever greater demands on hard disk drive manufacturers to reduce drive costs. In order to maintain market advantage, new hard disk drive designs typically incorporate greater efficiency in device operating tolerances or manufacturability.
There are basic components common to nearly all hard disk drives. A hard disk drive typically contains one or more disks clamped to a rotating spindle, a head for reading or writing information to the surface of each disk, and an actuator assembly utilizing linear or rotary motion for positioning the head for retrieving particular information or writing information to a particular location on the disk. A rotary actuator is a complex assembly that couples the head to a pivot point that sweeps the head across the surface of the rotating disk. The assembly typically couples the head to a flexible member called a suspension, which is then coupled to the pivotally mounted actuator assembly.
The current state of the art is to use one of two basic designs for attaching the suspensions with the actuator assembly: (1) the one-piece E-shaped block assembly (generally referred to as an E-block) or (2) the multi-piece assembly with unitary mounted suspension (generally referred to as Unamount). The E-block, typically made of aluminum or magnesium, is cast or extruded as a singular block element and machined to provide attachment points for suspensions (the attachment points form rigid arms). One or two suspensions are connected with each arm by swaging or staking through a machined bore in the arm which is aligned with a bore in the suspension. Swaging uses steel balls slightly larger in diameter than the machined bores to apply axial forces which deform and attach the suspensions to the arms.
Swaging applies force to the suspension and can deform a cantilevered portion of the suspension used to hold a slider on which a head is mounted. Deformation of the cantilevered portion of the suspension can lead to structural resonance variation and reduction in the reliability of ramp-based head loading and unloading. In order to control the amount of deforming force applied to the suspension with each impact, multiple steel balls with increasing diameters are often used in the swaging process. Damage can still result to the suspension. As data storage tracks are packed more tightly and as actuator arm block sizes shrink, requiring more precise performance of the actuator assembly, this problem will likely become acute, impacting future manufacturing yields. Further, it is difficult to maintain the preset spring rate and gram load of the suspensions during the swaging process, and suspension alignment and staking must be supervised and monitored, increasing the cost and decreasing the speed of assembly of the drives.
The Unamount assembly uses an actuator arm plate, typically stamped from a thin stainless steel sheet, that includes a circular bore that when coupled to spacer elements, forms a cylindrical bore designed to receive a bearing assembly. Each suspension is micro-spot welded to each actuator arm plate, which is then secured to the spacers and other such arm assemblies in a rigid manner to form the actuator assembly. The Unamount assembly has significant disadvantages including higher assembly cost, difficult assembly cleaning, potential for component damage during rework (the rigid assembly must be unfastened and the bearing assembly removed or exposed to detach a single arm plate), and less design flexibility due to the difficulty of structurally tuning the arm and suspension resonances at the same time.